The present invention pertains to the art of medical diagnostic imaging, particularly computerized tomographic (CT) scanners. The invention finds application in conjunction with volumetric, medical diagnostic imaging and will be described with particular reference thereto. However, it is to be appreciated that the invention also relates to single slice imaging, quality control examinations, and the like.
Heretofore, CT scanners have included a plurality of discrete radiation detectors arranged in a ring or rotatable ring segment around a patient examination region. Each discrete detector included a scintillation crystal which received radiation traversing a selected slice of a patient in the image region and converted the x-ray energy into light. A solid state photodiode or vacuum photomultiplier tube converted the light emitted by the scintillation crystal into electrical signals indicative of the intensity of emitted light, hence, the intensity of received radiation. By providing two rings of photodiodes or photomultiplier tubes back-to-back, two slices have been collected concurrently.
The use of discrete radiation detectors, such as photodiodes or photomultiplier tubes, has several drawbacks. First, installation is labor-intensive and expensive. Further, the prior art scintillation crystal/photodiode or photomultiplier tube assemblies tend to be relatively large and bulky which limits the density or number which may be disposed around the scan circle. The number of discrete crystal/photodiode units may also be limited by the sampling frequency and data processing capacity of the scanner.
Thick slices created when the entire face of each discrete detector received radiation suffered from visible partial volume effects. Narrow slices were created by screening part of the detector from receiving radiation. The flux limitations of the tubes required slower narrow slice scan times which lowered scanner throughput.
The present invention overcomes the above referenced problems and others.